A review of a new book compares gatherings of animals to human cities:

Sometimes we simply need to appreciate what’s right in front of us. “Cathedral termites in Australia,” Mr. Huling writes, “build mounds more than 15 feet tall, which, relative to their individual size, makes their buildings significantly larger than humanity’s tallest skyscraper is to us.” Dusky farmerfish in East Asia grow “crops” of red algae by assiduously “weeding out less palatable foods” and have effectively domesticated a type of shrimp whose waste fertilizes the algae and boosts yields.

Perhaps the most impressive discoveries are animal “cities,” including two assemblies of octopuses, dubbed Octopolis and Octlantis, found off the east coast of Australia. Some gatherings even qualify as animal megapolises. A single atoll in the Seychelles serves as home to hundreds of thousands of tortoises, while millions of flamingoes flock annually to Lake Natron in Tanzania. The largest gathering of nonhuman mammals on earth takes place in Texas, where 20 million bats crowd into Bracken Cave near San Antonio. Their collective body heat raises the cave’s temperature to a sweltering 106°F, and the piles of guano beneath them are deep enough to bury the Statue of Liberty to her waist. All these congregations, Mr. Huling writes, represent “parallel societies with their own sophisticated life-worlds.”

The development of megacities in modern life could be viewed as an important human achievement. Bringing together that many people in one physical setting with some order and cooperation is remarkable.

But animals have done this for a long time. Many animals, in different kinds of habitats, come together in large numbers.

This gets at a longstanding question: what makes humans unique? And we can take it another direction: what makes human cities unique? The hint above is that perhaps cities are not unique to humans, even as the gatherings may not look like cities in terms of what humans expect to see.

Or what is unique about cities? Are they just large collections of people? Is there a unique urban experience or way of life? Can humans do things in cities they cannot do elsewhere? Are cities scaled up versions of smaller communities?

Understanding the large gatherings of animals could help us better grasp about what large numbers of humans living together and interacting with each other are really about.